1. Field of the Invention
The invention relates to a data processing apparatus which can execute a power saving function process when a bi-directional communication is performed to a printing apparatus through a predetermined communication medium. The invention also relates to a data processing method for such a data processing apparatus and to a memory medium in which a computer readable program to realize such a data processing method has been stored.
2. Related Background Art
Hitherto, a state of a printing apparatus is detected between an external apparatus such as a host computer or the like and the printing apparatus for a period of time except for a period during a printing process. That is, by always performing a bi-directional communication, the external apparatus such as a host computer or the like detects various states such as absence of papers, door-open, low toner amount, and the like and notifies the operator of them by a screen of the host or the like. As such a system, a WPS (Windows Printing System) has already existed. Specifically speaking, a state change information of the printer side is held in a part of a print buffer on the printer side and a printer monitor on the host side inquires it at predetermined intervals. In this case, for example, a centronics interface is used.
The above conventional system, however, has a problem such that in the external apparatus such as a host computer or the like having a power saving function, such a function does not normally operate.
The power saving function of the external apparatus such as a host computer or the like operates when the user validly sets such a function and a device access to a keyboard, a serial port, a parallel port, a hard disk, or the like does not occur.
When the bi-directional communication is always executed to the printing apparatus, however, since the apparatus accesses to the parallel port, even if the user validly sets the power saving function, the function does not normally operate. That is, there is a problem such that the process of system software to control the printing apparatus invalidates the power saving function of the external apparatus such as a host computer or the like and obstructs the operation.